Study On Mechanical Properties Of Shear Thickening Gel And Nonlinear Spring

Shear Thickening Gel?STG?is a kind of amorphous linear polymers.In usual,it looks like the putty and possesses the flow characteristic.It is rapid hardening,which behave like the solid-like while bearing an impact force.When the force is removed,it transforms back to the initial state.STG has been widely used in the field of shock absorption and protection.Due to much of the energy was absorbed in the process of liquid-solid transformation.The research focused on the mechanical properties and performance improvement is still in the primary stage.Especially,the part of the corresponding relationship for energy absorption capacity and mechanical properties is not deep enough.Firstly,the mechanical parameters of STG changed with shear strain amplitude,excitation frequency in shear mode was studied by using the rheometer.And the correlation of energy absorption capacity and viscoelasticity were acquired.Then,the STG with excellent properties could be achieved by the doping inorganic particles.At the same time,the influence factors of STG mechanical properties were analyzed.Finally,STG nonlinear spring was designed by the STG,which has been modified.The STG nonlinear spring has ability of damping and stiffness self-coordination.This dissertation is focuses on studying the rheological properties of STG in shear modes and nonlinear spring.It was of great importance to evaluate the STG material,understand the STG material and study the structure deformation of the STG.The main research contents and result s are as follows:1)The demarcation of linear and nonlinear regions of STG materials and viscoelasticity tested by the large amplitude oscillatory shear?LAOS?experiment.The stress-strain curves for strain sweeping were analyzed.It was showed that the shear strain amplitude of 2% was critical point of strain,the STG from the linear region to the nonlinear region.STG was changed from liquid-like to solid-like at the critical conversion frequency?7 Hz?.In the area of liquid-solid transformation,STG achieves an excellent performance of energy absorption.2)The mechanical properties of STG were modified by inorganic particles?CaCO₃,SiC,ZrO2?.The STG was doped by the same particles with different mass fraction and mass fraction of different particle.In shear mode,they were tested by using the rheometer.Viscoelasticity and its corresponding stress-strain curve were analyzed by the changes of modulus,loss factor and complex viscosity.It was found that CaCO₃ has obvious advantages in terms of the improvement of mechanical properties3)The STG nonlinear spring possesses the ability of adaptive variable stiffness and damping characteristics.Under the condition of uniaxial compression test,the spring maximum stiffness was 7 N/mm.At 10 Hz frequency,the biggest STG spring stiffness was 98 N/mm,which was the 14 times of the uniaxial compression test.With the increase of frequency,hysteresis curve shape becomes more and more full.STG spring possesses very strong frequency sensitivity.In order to applying STG for better use in the areas of shock protection,the linear and nonlinear regions of STG materials were demarcated.In the region of STG nonlinear viscoelastic,STG internal organization structure was damaged,which needs to avoided in the shock absorption area application.STG nonlinear spring has good flexible performance with low frequency vibration,and has good variable stiffness characteristic with violent vibration.It further promotes the development of STG practical application.